Just like a northern team playing in the warm humid south, a southern team is at a disadvantage playing in the cold/windy/wet north. The Chicago Bears wilted badly in the 2nd half earlier this year in a game in Miami. There were numerous players cramping up for the Bears.
You can only add some much weather gear and it doesn't do much help when you have been out in it for 2.5 hours if you are not acclimated to it.